84 lines
2.8 KiB
C
84 lines
2.8 KiB
C
#include "material.h"
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#include "hittable.h"
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#include "utils.h"
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#include "vec3.h"
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#include <assert.h>
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#include <math.h>
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bool material_scatter(const Material *material, Ray r,
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const struct HitRecord *record, Color *attenuation,
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Ray *scattered) {
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switch (material->type) {
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case MATERIAL_LAMBERTIAN:
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return lambertian_scatter((const Lambertian *)material, r, record,
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attenuation, scattered);
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case MATERIAL_METAL:
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return metal_scatter((const Metal *)material, r, record, attenuation,
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scattered);
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case MATERIAL_DIELECTRIC:
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return dielectric_scatter((const Dielectric *)material, r, record,
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attenuation, scattered);
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}
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return false;
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}
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bool lambertian_scatter(const Lambertian *lambertian, Ray r,
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const HitRecord *record, Color *attenuation,
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Ray *scattered) {
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(void)r;
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Vec3 scatter_direction = vec3_add(record->normal, vec3_random_unit_vector());
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/* Catch degenerate scatter direction */
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if (vec3_is_near_zero(scatter_direction))
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scatter_direction = record->normal;
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*scattered = (Ray){record->p, scatter_direction};
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*attenuation = lambertian->albedo;
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return true;
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}
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bool metal_scatter(const Metal *metal, Ray r, const struct HitRecord *record,
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Color *attenuation, Ray *scattered) {
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Vec3 reflected = vec3_reflect(vec3_normalize(r.direction), record->normal);
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assert(metal->fuzziness <= 1);
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*scattered = (Ray){
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record->p,
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vec3_add(reflected,
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vec3_mul(metal->fuzziness, vec3_random_in_unit_sphere())),
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};
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*attenuation = metal->albedo;
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return vec3_dot(scattered->direction, record->normal) > 0;
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}
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static double schlick_reflectance(double cosine, double eta) {
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double r0 = (1 - eta) / (1 + eta);
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r0 *= r0;
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return r0 + (1 - r0) * pow(1 - cosine, 5);
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}
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bool dielectric_scatter(const Dielectric *dielectric, Ray r,
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const struct HitRecord *record, Color *attenuation,
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Ray *scattered) {
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*attenuation = (Color){1.0, 1.0, 1.0};
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double refraction_ratio =
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record->front_face ? (1.0 / dielectric->eta) : dielectric->eta;
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Vec3 unit_direction = vec3_normalize(r.direction);
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double cos_theta =
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fmin(vec3_dot(vec3_neg(unit_direction), record->normal), 1.0);
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double sin_theta = sqrt(1.0 - cos_theta * cos_theta);
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bool cannot_refract = refraction_ratio * sin_theta > 1.0;
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Vec3 direction;
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if (cannot_refract ||
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schlick_reflectance(cos_theta, refraction_ratio) > random_double())
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direction = vec3_reflect(unit_direction, record->normal);
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else
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direction = vec3_refract(unit_direction, record->normal, refraction_ratio);
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*scattered = (Ray){record->p, direction};
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return true;
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}
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